Tapper means for reciprocating air column sifter



Jan. 30, 1968 H. o. SUHM 3,366,237

TAPPER MEANS FOR RECIPROCATI NG AIR COLUMN SIFTER Filed Oct. 21, 1966 2 Sheets-Sheet 1 INVENTOR HOWARD O. SUHM ATTORNEY Jan. 30, 1968 H. O. SUHM TAPPER MEANS FOR RECIPROCATING AIR COLUMN SIFTER Filed Oct. 21. 1966 2 Sheets-Sheet 2 IIIII WW JMWHIINIIIIHHH I I ll will INVENTOR HO WARD O. S UHM AT TOR N E Y United States Patent Ofiice 3,366,237 Patented Jan. 30, 1968 3,366,237 TAPPER MEANS FOR RECIPROCATING AIR COLUMN SIFTER Howard 0. Suhm, New Berlin, Wis., assignor to Allen- Bradley Company, Milwaukee, Wis., a corporation of Wisconsin Filed Oct. 21, 1966, Ser. No. 588,568 4 Claims. (Cl. 209-237) ABSTRACT OF THE DISCLOSURE A reciprocating air column sifter includes a cabinet defining an operating chamber with fioor, and a sieve assembly is in the chamber on the floor. The floor comprises a lower relatively rigid plate provided with an opening directly under the sieve assembly and an upper relatively flexible cover sheet which extends completely over the surface of the floor. A tapper means is provided below the floor and includes a block received in the opening in the plate for vertical movement against the underside of the cover sheet, the block including an annular stop flange which extends laterally under the plate around the opening and is engageable therewith to limit upward movement of the block. A support bracket is connected to the floor and is stepped to define opposite horizontal stop portions spaced below the plate on opposite sides of the opening, the block stop flange being engageable with the stop portions to prevent the block from moving downwardly out of the opening. The bracket includes a central portion substantially directly under the block which mounts a plunger that is adapted to deliver pe riodical mechanical blows to the sieve assembly through the block and cover sheet. There is a bias means which operates between the central bracket portion and the block to hold the block against the cover sheet.

This invention relates to reciprocating air column sifters, and resides more particularly in a sifter incIUding tapper means operable on the sieve assembly of the sifter to insure effective sifting of extremely fine particles.

A reciprocating air column sifter of the type contemplated herein is shown in the co-pending application of Howard 0. Suhm et al., Ser. No. 473,949, filed July 22, 1965. In general, this type of sifter includes a cabinet defining an operating chamber with a floor, a sieve assembly including one or more sieves that rests on the floor of the chamber, and a speaker or other sonic vibrator that is above and faces the sieve assembly and is operable to establish reciprocating air movement therethrough to aid in sifting material down through the sieve or sieves.

Reciprocating air column sifters have proven highly effective for a wide range of uses. One particular advantage of this type of sifter is that for particles in all ordinary size ranges it is unnecessary to provide a mechanical hammering action to keep the sieve screens clear, thus minimizing operating noise and the possibility of mechanical damage. For extremely fine particles, however, for example particles of five to thirty-seven microns which are completely out of the operating range of usual sifters even with mechanical hammering action, a controlled, relatively light tapping action is sometimes desirable to insure against a build-up of fine deposits on the screens which might ultimately hamper sifting.

It is the object of this invention to provide tapper means for a reciprocating air column sifter which insures effective sifting of extremely fine particles, the arrangement provided being highly efiicient, easily controllable and adapted to operate without undue mechanical stress on the sifter, while still being relatively simple and inexpensive.

showing the The several advantages of the invention will be apparent from the description to follow. In the description, reference is made to the accompanying drawings, which form a part hereof, in which there is shown, by way of illustration and not of limitation, a preferred embodiment of the invention.

In the drawings:

FIG. 1 is a front view in elevation, with parts shown broken away and in cross section, of a reciprocating air column sifter including tapper means formed according to the invention,

FIG. 2 is an enlarged fragmentary view in cross section taken through the plane 22 shown in FIG. 1,.and

FIGv 3 is an enlarged fragmentary front view in elevation, with parts shown broken away and in cross section, elements of the tapper means of the sifter of FIG. 1.

The sifter of FIG. 1 is basically the same as that shown in the aforementioned co-pending application Ser. No. 473,949, to which reference may be had for a complete description. For the purposes hereof, it is sufficient to has a horizontal floor 3.

Removably disposed within the operating chamber 2 is a sieve assembly designated generally by the reference numeral 4. The portion of the cabinet 1 below the operating chamber 2 houses suitable controls as well as the elements of the tapper means to be described. A speaker (not shown) is'housed in the cabinet 1 above and facing the top of the sieve assembly 4 and is operable to establish reciprocating air movement therethrough. A vertically slidable door 5 is adapted to close off the front of the operating chamber 2 during operation.

The sieve assembly 4 comprises a stack of sieves 6, each sieve 6 comprising a split, rigid ring 7 and a screen 8 secured between the two parts thereof, the screens 8 of the several sieves 6 being graduated with the most open mesh on top. The sieves 6 are preferably of the stepped, interlocking type shown and described in the co-pending application of Frank A. Grabarczyk, Ser. No. 474,065, filed July 22, 1965, to which reference may be had for a further description.

Below the sieves 6 is a spacer 9 which has the same general configuration as the sieve rings 7 but is not split or provided with a screen 8. Above the sieves 6 is a rigid, conical funnel ring 10 which is directly under the sonic vibrator.

Below the spacer 9 is a rigid metal frame 11 which comprises a spider-like base 12, seen in phantom lines in FIG. 2, three spaced posts 13 and an upper ring 14 which receives and supports the spacer 9. The frame 11 also supports a thin rubber fines bag 15 which opens upwardly and has its upper periphery clamped between the ring 14 and spacer 9 and its closed lower end attached to the frame base 12.

The sieve assembly 4 also includes a clamp 16 of the type shown and described in the co-pending application of Frederick P. Loock et al., Ser. No. 473,961, filed July 22, 1965 to which reference may be had for a complete description. The clamp 16 is operable to hold the sieve assembly 4 together and in place on the floor 3 and also to clamp the severalelements of the assembly 4 together for insertion into and removal from the cabinet 1. It includes an upper ring portion made up of an upper and outer ring 17 and an inner or lower ring 18 telescoped in the ring 17, the rings 17, 18 being biased vertically apart by springs 19 interposed therebetween. When the sieve assembly 4 is in place, the upper ring 17 bears against the ceiling 20 of the operating chamber 2 and the lower ring 18 bears against the top of the funnel 10, the springs 19 then serving, in effect, to hold the entire sieve assembly 4 against the floor 3 and to hold the elements of the assembly 4 together to form what is essentially a rigid unit. A thin rubber diaphragm 21 is clamped between the funnel and lower clamp ring 18 to seal off the top of the sieve assembly 4. The clamp 16 is further provided with two bail members 22 which are attached to and depend downwardly from the ring 17, and which are adapted to be pulled downwardly and hook under the frame ring 14 to hold the entire sieve assembly 4 together for insertion into and removal from the chamber 2. The bail members 22 are inwardly offset and extend under the ring 18 to limit separation of the rings 17, 18.

As can be seen most clearly in FIGS. 2 and 3, a pair of locating studs 23 extend upwardly from the operating chamber floor 3 and are engageable with the periphery of the frame base 12 to locate and orient the sieve assembly 4 directly under the sonic vibrator at about the center of the floor 3. An arm 24 is pivotally mounted on the floor 3 and is movable between the positions shown in full and in broken lines in FIG. 2. The arm 24 serves as a third locating stud, and also as the actuating arm for a safety switch (not shown) of any conventional design, for example, a cam operated switch, which is connected in an operating circuit for the sitter. When the arm 24 is in the full line position ofFIG. 2, the circuit will be opened so that the sifter cannot be operated. When the sieve assembly 4 is slid into place, however, the frame base 12 will engage the arm 24 to pivot it to the broken line position shown in FIG. 3, which causes the safety switch to be closed allowing the sifter to be operated. As indicated, the arm 24 also serves as a third locating stud, and its rotation is preferably limited so that it cannot pivot past the broken line position shown in FIG. 2.

In operation, material to be sifted is introduced into the funnel 10 and the sieve assembly 4 is then inserted in the operating chamber 2. The speaker is operated to establish a reciprocating air movement through the assembly 4, which aids in sifting material down through the sieve screens 8. Fines are collected in the bag which, as previously indicated, is formed of thin resilient material to accommodate air movement generated by the speaker.

As can be seen most clearly in FIG. 3, the floor 3 is oftwo layer construction, and includes a lower, relatively thick supporting plate 25, which is preferably formed of steel of sufficient thickness to give substantial rigidity. Above and overlaying the plate 25 is a relatively thin, flexible cover sheet 26 which is preferably formed of stainless steel and on which the sieve assembly 4 actually rests. The support plate 25 is cut out to define a circular opening 27 substantially directly under the center of the frame base 12. As can be seen in FIG. 3, the periphery of the underside of the base 12 is cut away slightly, so that only a central portion directly over and slightly larger than the opening 27 actually rests on the floor 3.

A stepped bracket 28, formed of a strip of steel of sufiicient thickness to have substantial rigidity, is disposed in the cabinet 1 below the floor 3. The bracket 28 defines opposite upper horizontal portions 29 which are secured, for example by welding, to the underside of the plate 25 to mount the bracket 28 on the floor 3. Inwardly of the portions 29, the bracket 28 is offset to define opposite intermediate horizontal stop portions 30 adjacent and on opposite sides of the opening 27, and a central lower horizontal portion 31 which is substantially directly under the opening 27.

A circular tapper block 32, which is preferably formed of a relatively hard, shock resistant plastic material, is substantially co-extensive with and is guidingly received in the opening 27 to lie against the underside of the cover sheet 26 immediately below the center of the frame base 12. The block 32 is provided at its lower surface with an annular stop flange 33 which extends laterally outwardly of the opening 27 to lie between the support plate 25 and the bracket stop portions 30 with both of which it is engageable to limit upward and downward movement of the block 32. The spacing between the bracket portions 30 and the plate 25 and the thickness of the flange 33 are selected so that the block 32 cannot move upwardly far enough to damage the thin sheet 26 during a tapping action, and so that the block 32 cannot move downwardly far enough to move out of the opening 27. A compression Spring 34 is seated in a circular groove 35 formed in the underside of the block 32 and operates between the block 32 and the central bracket portion 31 to urge the block 32 upwardly against the sheet 26.

Attached to and depending from the underside of the central bracket portion 31 is a conventional solenoid 36 which has an extensible and retractible plunger 37 that extends upwardly through an opening in the central bracket portion 31 and faces the central portion of the underside of the block 32.

The plunger 37 is normally in the lower or retracted position shown in full lines in FIG. 3 Where its upper end is downwardly spaced from the underside of the block 32. Upon energization of the solenoid 36, however, the plunger is extended to the position shown in dotted lines'in FIG. 3, where it delivers a mechanical blow or tap to the block 32. The force of this blow is transmitted through the block 32. and sheet 26 to the frame base 12 and, since the sieve assembly 4 comprises what is essentially a rigid unit, is transmitted to the several screens 8, insuring that they will remain clear. The solenoid 36 may of course easily be actuated and controlled through known circuitry to establish the desired timing and amplitude for the tap delivered by the plunger 37. The resilient holding action afforded by the clamp 16 is important in that it insures that the sieve assembly 4 will not separate or bounce during tapping, although other holding means could be used or the weight of the assembly 4 itself may be sufiicient for holding under proper circumstances.

The tapper arrangement shown is relatively simple and inexpensive but is quite effective, enabling a sifter of the type shown to handle extremely fine particles down to sizes ranging from five to thirty-seven microns. A number of features contribute to this effectiveness. The two layer construction of the floor 3 is, for example, advantageous in that the heavy plate 25 provides the required rigidity and defines the opening 27 which guides the block 32, while the flexible cover sheet 26 is movable to transmit the tap effectively. The block 32 insures that the tap Wlll be evenly transmitted and, because of its relatively large surface area, prevents damage to the relatively thin sheet 26. Having the periphery of the underside of the frame base 12 cut away insures that the central portion will be against the floor 3 so that the full force of the tap will be transmitted to the sieve assembl 4. The spring 34 holds the block 32 against the sheet 26 to help insure that the full force of the tap is delivered and to prevent damage to the sheet 26. The block flange 33, support plate 25 and bracket stop portions 30 further ensure effective operation by limiting upward movement of the block 32 to prevent damage to the sheet 26 and by stopping downward movement before the block 32 can come out of the opening 27 and become misaligned. The stepped bracket 28 serves the multiple functions of mounting the solenoid 36, guiding the plunger 37, serving as a seat for the spring 34, serving as a limit to downward movement of the block 32, and mounting the entire assembly on the floor 3.

Although a preferred embodiment of the invention has been shown and described herein, it will be obvious that modifications might be made in the embodiments shown without substantial departure from the invention. It is not intended, therefore, that the invention be limited by the showing and description herein, or in any other way,

except insofar as limitations appear specifically in the following claims.

I claim:

1. In a reciprocating air column sifter the combination comprising: means forming an operating chamber with a floor, said fioor comprising a lower, relatively rigid plate with an opening therethrough and an upper, relatively flexible cover sheet which extends entirely across the opening; a sieve assembly on the floor substantially directly above the opening; and tapper means disposed below the fioor adapted to be actuated periodically to deliver a mechanical blow to the sieve assembly, said tapper means including a vertically movable block which is received in the opening and engageable with the underside of the cover sheet and a plunger that is adapted to deliver periodic blows to the block, the force of the blows being transmitted through the block and the floor to the sieve assembly.

2. The combination of claim 1 wherein the rapper means includes a supporting bracket that is connected to the floor and that defines opposite horizontal stop portions spaced below the rigid plate on opposite sides of the opening therethrough; and wherein the block includes stop flange means near its bottom surface that extend laterally outwardly to lie between and be engageable with the plate and bracket stop portions to limit vertical movement of the block.

References Cited UNITED STATES PATENTS 1,395,833 11/1921 Weidlein et a1. 300

2,029,848 2/1936 Wettlaufer 209347 X 2,211,000 8/1940 Brown et a1. M 209347 2,730,236 1/1956 Missien 209237 2,865,505 12/1958 Bruningh-aus 209-368 X 3,045,817 7/1962 Ward 209-318 X OTHER REFERENCES Allen-Bradley Sonic Sifter, Pub. 6901, the Allen- Bradley Co., Milwaukee, Wis, August 1965, pp. 209-237.

HARRY B. THORNTON, Primary Examiner.

TIM R. MILES, Examiner. 

